1. Field of the Invention
The present general inventive concept relates to a projection display which modulates a plurality of light beams having different colors so as to be suitable for image information and magnifies and projects the modulated light beams to display a color image.
2. Description of the Related Art
Projection displays include optical modulators for modulating light to be suitable for image information and illumination units for illuminating the optical modulators. A metal halide lamp, a super-high voltage mercury lamp, or the like has been used as an illuminating unit. However, these lamps have short life spans of several thousands of hours at most. Hence, when conventional projection displays including these lamps are used, these lamps need to be frequently replaced with new ones due to the short life spans. Also, the illumination units need color wheels to divide white light emitted from these lamps into red (R), green (G), and blue (B) light beams, so the illumination units are enlarged.
Recently, projection displays adopting compact light sources, such as a light emitting diode (LED), are under development. Japanese Patent Publication Nos. 2001-305658 and 2003-186110 disclose projection displays utilizing LEDs. LEDs emit relatively less light than a metal halide lamp or a super-high voltage mercury lamp. Accordingly, an array of LEDs is used as a light source of a projection display. To increase the amount of effective light incident upon a screen, the light is collimated before the light emitted from the LED is projected onto an optical modulator. In this case, a light-condensing efficiency is degraded due to characteristic of lenses that must be included in a condensing optical system.